Headlamp for motor vehicles

ABSTRACT

A headlamp for motor vehicles has a reflector, a discharge lamp located in front of the reflector, a glass envelope surrounding the discharge lamp and being transparent in certain sections to light of specific wavelengths, a lamp carrier which holds the discharge lamp so that the discharge lamp is arranged in a space limited at least by the lamp carrier and the glass envelope. The glass envelope blocks UV light in UV-A, UV-B and UV-C wavelength range.

BACKGROUND OF THE INVENTION

The present invention relates a headlamp for motor vehicles. Moreparticularly, it relates to a headlamp for motor vehicles which has adischarge lamp inserted into a reflector and surrounded by a glassenvelope which is transparent in certain sections to light of specificwavelengths.

Such a headlamp is disclosed in EP-A1-0 237 647. This headlamp has adischarge lamp whose discharge vessel is surrounded a glass envelopemade of hard glass. The discharge vessel is melt-sealed into the glassenvelope so that these parts are combined to form one unit. The spacebetween glass envelope and discharge vessel is evacuated. The glassenvelope is provided in certain sections with a coating which isnon-transparent and by means of which an asymmetrical light distributionrequired in dipped headlamps is achieved. By means of the glassenvelope, the UV-A light portion and UV-B light portion of the lighttransmitted by the discharge lamp is blocked to a specific degree since,due to its properties, glass generally inhibits the passage of theseportions. However, the UV-C light portion which is injurious to healthand also destroys plastics is not blocked by a glass envelope consistingmerely of customary glass. In addition, if the glass envelope is touchedwhen the headlamp is damaged, for example after an accident, there is arisk of combustion. The reason is that the high temperatures prevailingin the discharge vessel are transmitted to the glass envelope and if theelectrical terminals of the discharge lamp are touched there is a riskof lethal injury since the lamp is operated at a high voltage.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aheadlamp for motor vehicles, which avoids the disadvantages of the priorart.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a headlamp for motor vehicles, in which a discharge lamp isheld in a lamp carrier and arranged in a space limited at least by thelamp carrier and the glass envelope, wherein the glass envelope blockingUV light in the UV-Am UV-B and UV-C wavelengths range.

When the headlamp for motor vehicle is designed in accordance with thepresent invention it has, in contrast with the above, the advantage thatprincipally also the UV-C light portion is blocked by the glass envelopeand thus there is no risk of injury to health and no risk of destructionof plastic parts. In addition, the risk of combustion is reduced by theglass envelope since the discharge lamp cannot be touched directly butrather only the glass envelope, which reaches a substantially lowertemperature than the discharge lamp. The electrical terminals of thedischarge lamp are also prevented by the glass envelope from beingtouched.

In accordance with a further feature of the present invention,electrical conductor tracks are arranged on the outer surface of theglass envelope and are part of an electrical line which is connected toa lamp ballast serving to supply the discharge lamp with high voltage,and the discharge lamp is prevented from operating when the line isinterrupted. When the head-lamp is designed in accordance with thesefeatures, a further increase in safety is achieved since the dischargelamp cannot be operated with damaged conductor tracks and thus with adamaged glass envelope and also when the glass envelope is not mounted.In accordance with a further feature of the present invention, theheadlamp has a shutter with an optically effective edge and a lens isarranged in the direction of the light reflected by the reflector, sothat by means of the lens, an image of the edge of the shutter is formedas a light/dark border of the light distribution. The end of the glassenvelope pointing in the direction of emergence of light receives thelens, and the lens, like the glass envelope, blocks light in the UV-A,UV-B and UV-C wavelengths range. When the headlamp is designed inaccordance with these features, the glass envelope serves at the sametime as a holder for the lens. Still another feature of the presentinvention is that the conductor tracks of the glass envelope areconnected to an annular conductor section on the lens when the lens isinserted and are connected to one another via the section. With thesefeatures it is achieved that the discharge lamp cannot be operated whenthe lens is not inserted or is damaged. It is also possible that thereflector is constructed in a crown-like manner, with radially elasticresilient tops, between which the end region of the glass envelope canbe clamped. In this case the glass envelope can be easily mounted.

In the further development the cover is designed as a coating applied tothe glass envelope and therefore, the glass envelope serves at the sametime as a carrier of the cover so that no special component is requiredfor this.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first exemplary embodiment of a headlamp in a simplifiedview in longitudinal section,

FIG. 2 shows a glass envelope of the headlamp in FIG. 1 in a perspectiveview and

FIG. 3 shows a second exemplary embodiment with a headlamp according tothe projection principle in longitudinal section in a greatly simplifiedview.

DESCRIPTION OF PREFERRED EMBODIMENTS

A headlamp for motor vehicles illustrated in FIG. 1 with a firstexemplary embodiment has a housing 10 made of plastic. A reflector 11 isarranged in the housing. The light exit opening of the housing 10 iscovered with a front plate 12. A discharge lamp 14 which is held in alamp carrier 13 is inserted into the reflector 11 in its apex region andoperated at high voltage. The housing 10 has at its rear an opening 16through which the discharge lamp 14 can be inserted or removed and whichcan be closed off with a cap 17. The discharge lamp 14 is supplied withthe high voltage necessary for its operation from a lamp ballast 18driven by the electrical system of the motor vehicle. A pot-shaped glassenvelope 19 which is held in a receptacle 21 in the lamp carrier 13 isplaced, with spacing, over the part of the discharge lamp 14 projectingout of the lamp carrier 13 into the reflector 11. The discharge lamp 14is thus arranged in a space which is closed off by the lamp carrier 13and the glass envelope 19. The space between the discharge lamp and theglass envelope is larger than the diameter of the discharge vessel ofthe discharge lamp. The floor 22 of the glass envelope 19, pointing inthe direction of the light emerging from the reflector 11, is providedwith a non-transparent coating 23 so that the light emerging directlyforward from the discharge lamp 14 is screened. The glass material ofthe glass envelope 19 or a filter coating applied to the latter blocksin the UV-A, UV-B and UV-C range the UV light transmitted by thedischarge lamp 14 so that no damaging UV radiation acts on the housing10 or emerges from the headlamp.

The receptacle 21 for the glass envelope 19 in the lamp carrier 13 is ofcrown-like design with resilient tabs 24 arranged with a radial elasticbend on the circumference of said receptacle. The open end of the glassenvelope 19 provided with a radially outwardly pointing circumferentialprojection 26 can be locked in the tabs. However, the glass envelope canalso be mounted in the lamp carrier in a different way, for example in athread-like fashion.

Two conductor tracks 27 are diametrically opposite one another andextend parallel to the longitudinal axis 28 of the glass envelope fromits open end to its floor 22. They are arranged on the outer surface ofthe glass envelope 19. In front of the floor 22, the conductor tracks 27are connected to one another by means of a conductor section 29 engagingaround the circumference of the glass envelope. The conductor tracks 27,29 are evaporated on the glass envelope 19 and connected in series tothe lamp ballast 18 by a feed line from the electrical system of themotor vehicle via contacts in the receptacle 21, and are thus part ofthe feed line. Only the low voltage of the electrical system is appliedto the conductor tracks 27 through this circuit and the discharge lamp14 can only be operated with the glass envelope 19 inserted andconductor tracks 27, 29 intact. If the glass envelope 19 and thus theconductor tracks 27, 29 are damaged, the feed line to the lamp ballast18 is interrupted and it is not possible to operate the discharge lamp14.

The conductor tracks 27, 29 can also be part of a control line which isconnected to the lamp ballast 18. The operation of the discharge lamp 14is prevented by the lamp ballast when the control line 30 isinterrupted.

The glass envelope 19 prevents the discharge lamp 14 from being touchedduring operation. If the conductor tracks 27, 29 on the glass envelope19 are touched there is no risk of lethal injury, in contrast with thehigh-voltage terminals of the discharge lamp, which are howeverprevented from being touched by the glass envelope 19. In addition, theglass envelope 19 acts as a screen against glass pieces of the dischargelamp which are scattered in the event of a possible explosion of thedischarge lamp 14 filled with gas under high pressure.

A non-transparent coating 32 which serves to form a light/dark border inthe light distribution generated by the headlamp is applied in sectionsto the glass envelope 19. The coating 32 can be applied on the innersurface or outer surface of the glass envelope 19. The course of theedge 33 of the coating 32 is oriented to the desired course of thelight/dark border. In order to avoid an accumulation of heat, the glassenvelope 19 can be enlarged in the region of the coating 32.

In FIG. 3, a second exemplary embodiment is illustrated with a headlampaccording to the projection principle. This headlamp has a reflector 31in whose horizontal and vertical central section ellipses are produced.The discharge lamp 14 is inserted into the reflector 31 by means of thelamp carrier 13. A shutter 41 with an optically effective upper edge 42and a lens 43 which forms an image of the upper edge 42 of the shutter41 as a light/dark border of the light distribution is arranged in thedirection of the light reflected by the reflector 31. The discharge lamp14 is surrounded by a glass envelope 39 which, as described in the firstexemplary embodiment, is constructed as a UV filter and which isinserted into a receptacle 44 arranged at the front edge of thereflector 31. The shutter 41 is also held in the receptacle 44 andarranged within the glass envelope 39. The end of the glass envelope 39pointing in the direction of emergence of light receives the lens 43and, it is impossible for any UV radiation to emerge between glassenvelope 39 and lens 43. The lens 43 is constructed, like the glassenvelope 39, as a UV filter. The discharge lamp 14 is thus arranged in aspace limited by the lamp carrier 13, the reflector 31 and the glassenvelope 39 and the lens 43 and completely screened.

Two electrical conductor tracks 46 which extend parallel to itslongitudinal axis from the receptacle 44 to the front end of the glassenvelope 39 are arranged on the glass envelope 39 diametrically oppositeone another. On the lens 43, an annular conductor section 47 is arrangedpointing towards the glass envelope. Thereby the conductor tracks 46 areconnected to one another when the lens 43 is inserted into the glassenvelope 39. The conductor tracks 46 are connected by means of contactsin the receptacle 44 to the electrical line 30. As described in thefirst exemplary embodiment, it can be a feed line from the vehicleelectrical system or a control line to the lamp ballast 18. Thereceptacle 44 for the glass envelope 39 can, as described in the firstexemplary embodiment, also be constructed in a crown-like manner.

An additional reflector 49 is arranged adjacent to the reflector 31 inthe direction of emergence of light. It has no influence on the lightdistribution and serves to generate a desired apparent image of theheadlamp, for example a rectangular or round apparent image.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in aheadlamp for motor vehicles, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A headlamp for motor vehicles,comprising a reflector; a discharge lamp located in front of saidreflector; a glass envelope surrounding said discharge lamp and beingtransparent in certain sections to light of specific wavelengths; a lampcarrier which holds said discharge lamp so that said discharge lamp isarranged in a space limited at least by said lamp carrier and said glassenvelope, said glass envelope blocking UV light, in UV-A, UV-B and UV-Cwavelength range; a lamp ballast serving to support said discharge lampwith high voltage; electrical line connected said lamp ballast; andelectrical conductor tracks arranged on an outer surface of said glassenvelope and forming a part of said electrical line, said discharge lampbeing prevented from operating when said electrical line is interrupted.2. A headlamp as defined in claim 1, wherein said electrical line is apart of a feed line from an electrical system of the motor vehicle tosaid lamp ballast.
 3. A headlamp as defined in claim 1, wherein saidelectrical line is a control line formed so that an operation of saiddischarge lamp is prevented when said control line is interrupted bysaid lamp ballast.
 4. A headlamp as defined in claim 1, wherein saidglass envelope has a pot shape and a floor pointing in direction ofemergence of light, said floor being non-transparent, said conductortracks extending approximately parallel to a longitudinal axis of saidglass envelope and being connected to one another in the region of saidfloor.
 5. A headlamp as defined in claim 4; and further comprising anannular conductor section which connects said conductor tracks to oneanother in the region of said floor.
 6. A headlamp as defined in claim1; and further comprising a non-transparent cover provided on said glassenvelope to form a light/dark border in a light distribution generatedby the headlamp.
 7. A headlamp as defined in claim 6, wherein said coveris formed as a coating applied to said glass envelope.
 8. A headlamp asdefined in claim 1, wherein said glass envelope has a floor which isnon-transparent.
 9. A headlamp as defined in claim 1; and furthercomprising a shutter with an optically effective edge and a lensarranged in direction of the light reflected by said reflector and formsan image of said edge of said shutter as a light/dark border of a lightdistribution, said glass envelope having an end which points indirection of emergence of light, said end of the glass envelopereceiving said lens which blocks light in the UV-A, UV-B and UV-Cwavelength range.
 10. A headlamp as defined in claim 9, wherein saidlens has an annular conductor section, said glass envelope havingconductor tracks which are connected to said annular conductor sectionwhen said lens is inserted and are connected to one another by saidannular conductor section.
 11. A headlamp as defined in claim 10,wherein said conductor tracks are formed as evaporate conductor trackson said glass envelope.
 12. A headlamp as defined in claim 10, whereinsaid annular conductor sections are formed as an evaporated conductorsection on said lens.
 13. A headlamp as defined in claim 9, wherein saidlamp carrier has a receptacle, said glass envelope being inserted insaid receptacle.
 14. A headlamp as defined in claim 9, wherein saidreflector has a front edge provided with a receptacle, said glassenvelope being inserted in said receptacle of said front edge of saidreflector.
 15. A headlamp for motor vehicles, comprising a reflector; adischarge lamp located in front of said reflector; a glass envelopesurrounding said discharge lamp and being transparent in certainsections to light of specific wavelengths; a lamp carrier which holdssaid discharge lamp so that said discharge lamp is arranged in a spacelimited at least by said lamp carrier and said glass envelope, saidglass envelop blocking UV light, in UV-A, UV-B and UV-C wavelengthrange, said lamp carrier having a receptacle, said glass envelope beinginserted in said receptacle; conductor tracks arranged on said glassenvelope; and means for making contact with said conductor tracks andarranged in said receptacle.
 16. A headlamp for motor vehicles,comprising a reflector; a discharge lamp located in front of saidreflector; a glass envelope surrounding said discharge lamp and beingtransparent in certain sections to light of specific wavelengths; a lampcarrier which holds said discharge lamp so that said discharge lamp isarranged in a space limited at least by said lamp carrier and said glassenvelope, said glass envelop blocking UV light, in UV-A, UV-B and UV-Cwavelength range, said reflector having a front edge provided with areceptacle, said glass envelope being inserted in said receptacle ofsaid front edge of said reflector; conductor tracks arranged on saidglass envelope; and means for making contact with said conductor tracksand arranged in said receptacle.
 17. A headlamp for motor vehicles,comprising a reflector; a discharge lamp located in front of saidreflector; a glass envelope surrounding said discharge lamp and beingtransparent in certain sections to light of specific wavelengths; a lampcarrier which holds said discharge lamp so that said discharge lamp isarranged in a space limited at least by said lamp carrier and said glassenvelope, said glass envelop blocking UV light, in UV-A, UV-B and UV-Cwavelength range; and means forming a crown-like receptacle providedwith radially elastic resilient tabs, said glass envelope having an endregion which is clamped between said resilient tabs.